It is generally known that certain polymeric materials take up and retain most dyestuffs to an insufficient extent. Examples of such polymeric materials are polyalkylenes, more in particular poly-alpha-olefins such as polypropylene and polyethylene, and furthermore polyesters. The difficulty in dyeing these polymeric materials has had a restricting effect on their applicability to fibres, mono-filaments and foils.
Various possibilities have been proposed to increase the capacity of these polymeric materials to take up and retain dyestuffs. Thus it has been proposed to degrade the surface of the polymer slightly by oxidizing or radiation, by grafting or copolymerization and by incorporating suitable materials in the polymer. The incorporation of additives in the polymer is generally preferred because it avoids extra manufacturing steps. Moreover, the additive used may also impart secondary beneficial properties to the polymeric material.